在 2024/6/25 13:00, Anand Khoje 写道:
On 6/25/24 02:11, Jesse Brandeburg wrote:
On 6/24/2024 8:33 AM, Anand Khoje wrote:
--- a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
@@ -608,6 +608,7 @@ enum {
RELEASE_ALL_PAGES_MASK = 0x4000,
};
+#define MAX_RECLAIM_NPAGES -50000
Can you please explain why this is negative? There doesn't seem to be
any reason mentioned in the commit message or code.
At the very least it's super confusing to have a MAX be negative, and at
worst it's a bug. I don't have any other context on this code besides
this patch, so an explanation would be helpful.
Hi Jesse,
The way Mellanox ConnectX5 driver handles 'release of allocated pages
from HCA' or 'allocation of pages to HCA', is by sending an event to the
host. This event will have number of pages in it. If the number is
positive, that indicates HCA is requesting that number of pages to be
allocated. And if that number is negative, it is the HCA indicating that
that number of pages can be reclaimed by the host.
In this patch we are restricting the maximum number of pages that can be
reclaimed to be 50000 (effectively this would be -50000 as it is
reclaim). This limit is based on the capability of the firmware as it
cannot release more than 50000 back to the host in one go.
I hope that explains.
To be honest, I am also obvious why this MACRO is defined as a negative
number. From the above, I can understand why. I think, perhaps many
people also wonder why it is defined as a negative. IMO, it is better
that you put the above explanations into the source code as comments.
When users check the source code, from the comments, users will know why
it is defined as a negative number.
Thanks a lot.
Zhu Yanjun
Thanks,
Anand
